Databases Stefano Grazioli

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Databases Stefano Grazioli

Why do we need Databases? Program (e.g., VBA) data is volatile Data in one place for everyone to use Indispensable in commerce Database

DBs vs. DBMSs DBMS DataBase DataBase file(s) A database (DB) is an organized collection of data A DataBase Management System (DBMS) is a software that provides data-related functionality DataBase User location Data center User or program User or program ‘Client’ program DBMS DataBase file(s) DBMS: Access, Oracle, IBM DB2, SQL Server, MySQL...

DBs and the Web DBMS DataBase DataBase file(s) Web server User location Data center DataBase User or program Web server User or program Browser program DataBase file(s) DBMS

Relational DBMS RDBMS “tables inside” When a DBMS organizes your data so that they appear to the users as TABLES, that DBMS is a Relational DBMS, or RDBMS. I speak SQL “tables inside” I speak SQL RDBMS Client program

What Is New In Technology? WINIT What Is New In Technology?

Congratulations! You are hired at SmallBank Homework

You are a Business Intelligence analyst at SmallBank Welcome! So glad that you are here and can help us with Business Intelligence! I have so many business questions for you… (1) Who are our customers in Austin, TX? I need a list of first names, last names and IDs (2) What are the rates that we offered on our loans? Prepare a report with the loan IDs and rates for the loans under $50,000,000 (3) …. Please access our MS SQL Server and create these reports for me…

Accessing Business Data SmallBank data: Loan, Loan Officer, Customer, Insurance Plan User location Data center RDBMS MS SQL Server SQL Client Visual Studio Sql queries F-sg6m-s4 A file on the server

Example Table: Loan Officer ACTUAL TABLE DIAGRAM LO id f name l name phone demo

Small Bank DB: Data Dictionary Loan l_id = the loan unique id principal, rate, date_due, Loan officer lo_id = the loan officer’s unique id f_name, l_name, phone Customer c_id = the customer’s unique id f_name, l_name, city, state Insurance plan coverage = maximum amount covered premium = amount to pay every year

Reading the Data Model Primary key: a unique identifier used to retrieve the record

Reading the Relationships 1 6 “A loan officer has many loans, a loan has one loan officer” One 5 2 Many 3 4

SQL Queries

SQL Structured Query Language The standard language for databases 70s: - Codd - SEQUEL – Structured English QUEry Language commercialized it in 1979 1986 ISO/ANSI Sometimes sought as a required skill in interviews

SQL EXAMPLE: A QUERY SELECT First_Name, Last_Name, ssn FROM StudentTbl WHERE gpa > 3.0 ORDER BY Last_Name;

4+2 BASIC SQL COMMANDS SELECT = ‘search’ INSERT a new row UPDATE a existing row DELETE a row CREATE a table DROP a table

Navigating the Relationships (‘join’) FK foreign key: a PK in another table, used to link the two tables FK FK FK FK

Joins are commonsense If I give you c_id ‘4977’, can you give me the phone numbers of the loan officers for that client?

SQL Query Select loan_officer.phone from customer_in_loan, loan, loan_officer where customer_in_loan.c_id = '4977' and customer_in_loan.l_id = loan.l_id and loan.lo_id = loan_officer.lo_id If I give you c_id ‘4977’, can you give me the phone numbers of the loan officers for that client?